Recent findings suggest that in addition to causing a number of common respiratory diseases of children, the paramyxoviruses may be involved in multiple sclerosis and subacute sclerosing panencephalitis by means of persistent infections which involve a delicate balance between virus and host. Employing Newcastle disease virus (NDV), a model paramyxovirus, this project is concerned with the factors which control the conversion of the host cell from the production of host cell proteins to the production of virus-specific proteins and the effects which these proteins have on the infected cell. The biological effects of NDV infection can now be approached in terms of the biochemical events which cause them. In particular, the project involves: 1) characterization of the virus-specific messenger RNA under various conditions of infection; 2) correlations of messenger activity of specific messengers with specific proteins: 3) characterization of virus- specific proteins with particular reference to control, rates of synthesis, and processing; 4) analysis of cell membrane alteration; and 5) analysis of the effects of infection on host cell protein synthesis and pre-existing membrane proteins. Techniques to be used include: a) incorporation of radioactive precursors; b) cell and virus fractionation; c) fractionation of RNA and proteins by velocity sedimentation, column chromatography and acrylamide gel electrophoresis; and d) identification of virus-specific changes by immunological, biological, and biochemical procedures.